Montmorillonite-loaded nano zero-valent iron (MMT/nZVI) was prepared from montmorillonite (MMT)by liquid-phase reduction using nano zero-valent iron (nZVI). The experimental results showed that the adsorption process of perfluorooctane sulfonic acid(PFOS) by MMT/nZVI followed the pseudo-first-order kinetic model and Langmuir isotherm model. The theoretical maximum adsorption amount was 0.34 mg/g, which was 4.25 times higher than that of MMT (0.08 mg/g). MMT/nZVI exhibited better removal efficiency than MMT under different pH conditions, with the highest removal efficiency reaching 74.97% at pH 3. Additionally, the presence of Cl^- and SO₄^2- had minimal effects on PFOS removal, while CO₃^2- significantly inhibited the removal efficiency. In the presence of CO₃^2-, MMT showed almost no PFOS removal efficiency, whereas MMT/nZVI exhibited the maximum removal efficiency of 15.87%, suggesting that MMT/nZVI performed better than MMT under the interference of ions in solutions. The surface characterization results of XRD, FTIR and XPS, in combination with the results from sorption performance, demonstrated that MMT/nZVI mainly relied on hydrogen bonding, complexation and hydrophobic interactions for the adsorption removal of PFOS. The integration of nZVI enhanced the hydrophobicity of MMT and promoted the complexation reaction between PFOS and iron oxide minerals, which synergistically improved the adsorption performance of MMT/nZVI, resulting in the higher adsorption capacity for PFOS than that of MMT.